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RGB+Alpha background color
Why is it that when I render my animations RGB+alpha, sometimes they have a black background and sometimes they have a grey background?
I think the correct background color should be grey right?
Thanks
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2 Replies
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In my experience it seems to depend on 2 things:
1) The background colour of the composition in AE, &
2) The program you’re importing the file into.Some programs will fill an alpha channel with a random colour (like black, white or middle grey), some support the checkerboard look, while others simply ignore the alpha channel and use the RGB value. Sometimes a program will mistakenly interpret the alpha as Straight instead of Premultiplied, (or vice versa), which you can usually (but not always) change. After effects will usually (if not always) fill the transparent parts of a composition with the background colour.
AFAIK, there is no “correct” colour – it all depends on what you are planning to do with it.
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You’re right on the money.
When After Effects renders a RGB+A file, and it’s set as Premultiplied (matted), AE mattes alpha so it’s premultiplied with the background color.
Problem is, some video applications can only handle premultiplied alphas matted with black or white.
It’s not only that the background color will not be the one you expect. Worse than that, the transparency information will not be handled correctly, since the interpretation is based on a wrong assumption.
You can either set your Comp’s background color to pure black, or render with a straight alpha.Adolfo Rozenfeld · Adobe
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